A week after the violent siege at the U.S. Capitol and a week ahead of President-elect Joseph R. Biden Jr.’s inauguration, officials are bracing for uncertainty and preparing for the potential of violence in the days ahead.
On Tuesday night, Defense Department officials said that the Army secretary, Ryan McCarthy, had decided to arm National Guard members who will be deployed to protect the Capitol building complex as Mr. Biden is sworn into office.
Chief Robert J. Contee III of the Metropolitan Police Department said on Wednesday that he expected more than 20,000 members of the National Guard in the Washington metropolitan area on Inauguration Day. It remains unclear how many of the Guard members will carry weapons.
The number of troops may ultimately climb beyond 20,000; it has been rapidly increasing in recent days as intelligence officials monitoring pro-Trump groups online have grown increasingly worried that militant, far-right organizations have plans for violent protests in Washington.
The decision to arm the Guard members illuminates the gnawing uncertainty of the past week. Members of Congress expressed worry about their return to the Capitol after they were briefed on several active threats against them, and the F.B.I. has warned of possible violence at all 50 state capitol buildings.
Defense Department officials were meeting with Washington authorities on Wednesday to work on plans to try to ensure there is not a repeat of last week’s violent breach. The scope of the protests and the violence of the mob took law enforcement by surprise.
As federal officials worked to meet the security threat in Washington, the number of people who have been arrested on suspicion of involvement in the assault on the Capitol continued to climb.
Michael Sherwin, the acting U.S. attorney for the District of Columbia, said at a news conference on Tuesday that he expected hundreds of people would eventually be charged with crimes ranging from trespassing to seditious conspiracy and murder. He called the investigation into the attack on the Capitol “unmatched” in scope.
Pentagon officials said they were deeply worried about Inauguration Day next week. About 16 groups have registered to stage protests, and officials said that law enforcement agencies were preparing for the possibility of armed conflict.
For President Trump, the past week has included a flurry of rebukes from businesses and once-loyal politicians. Senator Mitch McConnell of Kentucky, who stood by the president during lesser controversies, told his associates that he believed Mr. Trump had committed impeachable offenses. The U.S. Chamber of Commerce, the nation’s largest business lobbying group, also admonished the president’s conduct.
The House impeached Mr. Trump, for the second time, on Wednesday with 10 Republicans breaking with the president.
— Will Wright, Helene Cooper and Hailey Fuchs The New York Times